1. Field of the Art
This invention relates to a surface flaw detector, and more particularly to a device for detecting any flaw existing in the surface of a substantially circular-sectioned rod- or bar-shaped material.
2. Description of the Prior Art
Welding rod is a typical example of a circular-sectioned material which is contemplated to be examined by the device of this invention. In manufacture of such welding rods, every produced rod is subjected to a visual test to check for any surface flaw at a stage immediately before the final packaging step so as to ensure the quality (commercial value) and specified performance of the welding rods in use.
The welding rods are likely to suffer flaws attributable to partial strip-off of the coating flux or development of cracks formed in the axial direction or ring cracks in the flux in their production process, particularly in the coating or drying step, so that it is essential to detect such flaws for ensuring the quality of the products.
Heretofore, the produced welding rods have been examined one by one visually by the inspector in the final step of the production process and sorted out according to the type and size of the flaw.
Such one-by-one rod surface visual inspection, however, is very time-consuming, and also fatigue of the inspector is multiplied as the inspection speed increases, resulting in a warped sense of judgment of the inspector or even misled inspection. Thus, there was a danger that the flawed welding rods be passed over and erroneously judged as conforming products.
Various kinds of surface flaw detectors utilizing the light beams have been proposed in U.S. Pat. No. 3,430,055 and many other patents, but none of these proposals provides a satisfactory solution to the above-said problems.